945 
 WTPZ44 KNHC 210844
 TCDEP4
 
 Hurricane Willa Discussion Number   5
 NWS National Hurricane Center Miami FL       EP242018
 300 AM MDT Sun Oct 21 2018
 
 Willa has continued to rapidly intensify based on a well-defined CDO
 with an intermittent pinhole eye evident in high-resolution GOES-16
 infrared (IR) satellite imagery. Upper-level outflow has become well
 established in all quadrants. The intensity is difficult to
 ascertain since satellite intensity estimates vary widely based on
 the scene type used and also the small size of the hurricane. TAFB
 and SAB both provided an estimate of T4.0/65 kt, whereas UW-CIMSS
 ADT and SATCON were 67 kt and 56 kt, respectively. In contrast, NHC
 objective T-numbers are T5.0/90 kt using an embedded center and as
 high as T6.0/115 kt using a pinhole eye. Given that the eye has not
 been maintained in IR imagery, the advisory intensity of 75 kt lies
 between the subjective TAFB/SAB estimate and lower NHC objective
 estimate.
 
 Willa is moving at 315/06 kt. There is no significant change to the
 previous forecast track reasoning. Willa is forecast to continue
 moving northwestward for the next 24 h or so, followed by a turn
 toward the north on Monday, with a motion toward the northeast
 expected on Tuesday as the hurricane gradually rounds the western
 periphery of the deep-layer ridge. By late Tuesday, Willa is
 forecast to accelerate northeastward ahead of a deep-layer trough
 that will be approaching Baja California, resulting in landfall
 along the west-central coast of Mexico on Wednesday. The latest 00Z
 model guidance is tightly packed about the previous forecast track,
 and only minor forward speed adjustments were required. A 96-h
 position has been provided only for continuity purposes, and Willa
 will likely have dissipated over the Mexican mountains by then.
 
 Willa's small inner-core wind field along with ideal environmental
 conditions consisting of low shear, high mid-level moisture, and
 warm SSTs of 28 deg C should allow the hurricane to continue to
 rapidly intensify for the next 24-36 hours, followed by a leveling
 off in the intensity by early Tuesday due to expected cold upwelling
 beneath the slow-moving hurricane.  In 60-72 hours, increasing
 southwesterly shear ahead of the aforementioned deep-layer trough is
 expected to induce steady weakening until landfall occurs. Rapid
 dissipation over the mountainous terrain of mainland Mexico will
 occur after landfall. The official intensity forecast is a tad
 above the consensus models HCCA and FSSE, and is little below the
 robust Navy COAMPS-TC model forecast.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  21/0900Z 16.2N 106.5W   75 KT  85 MPH
  12H  21/1800Z 16.8N 107.0W   85 KT 100 MPH
  24H  22/0600Z 17.6N 107.4W  100 KT 115 MPH
  36H  22/1800Z 18.7N 107.7W  115 KT 130 MPH
  48H  23/0600Z 19.8N 107.7W  120 KT 140 MPH
  72H  24/0600Z 22.3N 106.1W   90 KT 105 MPH...NEAR WNCTRL MEXICO
  96H  25/0600Z 26.9N 101.2W   25 KT  30 MPH...INLAND NCNTRL MEXICO
 120H  26/0600Z...DISSIPATED INLAND
 
 $$
 Forecaster Stewart